Gas driven hydraulic actuator



June 28, 1960 J. D. MOELLER ETAL 2,942,553

GAS DRIVEN HYDRAULIC ACTUATOR Filed May 9, 1958 s Sheets-Sheet 1 I! if 4% In 6! INVENTORS Jomv .D. Mae-um 17 7:0 R. 5CARFF BY M THEIR AT ORIVEY June 28, 1960 J. D. MOELLER ETA!- 2,942,553

GAS DRIVEN HYDRAULIC ACTUATOR Filed May 9, 1958 3 Sheets-Sheet 2 4 10 w w 14: w l W 1/0 7;; Z INVENTOR JOHN D. MOELLER w BY 7'50 R. SCARFF D. C S

THE/R ATTORNEY June 28, 1960 J. D. MOELLER ETA!- 2,942,553

GAS DRIVEN HYDRAULIC ACTUATOR Filed May 9, 195a s Sheets-Sheet s lakl H 14 v is JOHN D. OELLER BY 750 A. .ScARFF 71 5 D THE/R ATTORNEY GAS DRIVEN HYDRAULIC ACTUATOR John D. Moeller, Dayton, and Ted R. Scarfl, Troy, Ohio, assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed May 9, 1958, Ser. No. 734,185

4 Claims. (Cl. 103-49) This invention relates to pumps, and particularly to gas driven hydraulic pumps.

At the present time there is a demand for efiicient, high pressure pumping systems for use in missiles. The present invention relates to a reciprocating pump system actuated by gaseous fluid medium'for producing a source of hydraulic fluid under high pressure which is reliable, of minimum weight and is highly eflicient. Accordingly, among ,our objects are the provision of a reciprocating type gas driven hydraulic pump; the further provision of an inertia balanced reciprocating gas driven hydraulic pump; and the still further provision of a partial admission reciprocating gas driven hydraulic pump.

The aforementioned and other objects are accomplished in the present invention by employing opposed reciprocating piston assemblies which are interconnected for movement in the same directions, and valve means controlled by the pistons for controlling the admission of gas to opposite cylinders so as to maintain the pistons in a state of continuous reciprocation. Specifically, in all of the embodiments disclosed herein the motor and pumping pistons are formed as an integral assembly, and the diameter of the motor pistons is twice the diameter of the pumping pistons. Each motor and pumping piston assembly is mounted for reciprocation in a cylinder having a stepped bore, and the combined motor and piston assemblies are interconnected by a plurality of rods so as to move simultaneously in the same direction. One of the interconnecting rods has a saddle, or valve actuator, thereon for actuating one or the other of a pair of pilot valves adjacent the stroke ends of the two motor and pumping piston assemblies.

Gas from any suitable source, such as a solid fuel propellant tank, is supplied to a servo actuated reversing valve. The supply gas pressure is controlled by a relief valve so as to maintain it within predetermined limits, i.e., between 700 and 800 p.s.i. The reversing valve controls the admission and exhaust of gas to the motor chambers, and the position of the reversing valve is con-' trolled by the mechanically and servo actuated pilot valves.

The pumping chambers are connected by passages through suitable one-way inlet check valves to a reservoir of hydraulic fluid, and likewise connected by passages through one-way outlet check valves to a delivery conduit. The hydraulic pressure in the delivery conduit may be controlled by any suitable pressure regulating valve. In the full admission embodiment, the hydraulic fluid will be discharged at a pressure directly proportional to the ratio between the areas of the pumping and motor pistons, and thus with a supply gas pressure between 700 and 800 p.s.i., the delivery pressure of the pumps will be between 2800 and 3200 p.s.i.

In the partial admission hydraulic pumping system, an additional servo actuated shuttle valve is incorporated in the system, which shuttle valve is actuated by a predetermined movement of the motor pistons so as to 2,942,553 Patented June 28, 1960 interrupt the supply of gas under pressure to the motor chamber and thereafter allow the gas in the motor chainher to expand thereby reducing the pressure thereof. In the partial admission system, a gas supply having a higher pressure can be utilized to obtain the same pressure in the hydraulic fluid delivery conduit as in the full admission system using a lower gas supply pressure.

In a third embodiment, a second pair of motor and pumping pistons are actuated in an opposite direction to the first set of motorand pumping pistons so as to bal ance out the inertia effects of the reciprocating system. In this instance, the combined outputs of the pumps are connected in parallel, and movement of the second set eating pump constructed according to one embodiment of 25 I this invention.

Figure 2 is a schematic view similar to Figure 1 illustrating the partial admission gas actuated hydraulic pumping system. Figure 3 is a schematic view illustrating the inertia balance gas actuated pumping system.

With particular reference to Figure 1, the pump mechanism comprises a pair of opposed cylinders 10 and 20 of stepped diameter. The cylinders '10 and 20 contain piston assemblies 12 and 22, respectively. The piston 12 has head portions; 14 and 16 which are received in the stepped diameter bore of the cylinder 10, and the piston 22 has head portions 24. and 26 received in the stepped diameter bore of cylinder 20. The piston assemblies 12 and 22 dividetheir respective cylinders into motor chambers '18 and 2S and pumping chambers 19 and 29, respectively. Moreover, in the disclosed embodiments, the diameter of the piston head portions 14 and 24 is twice the diameter of the piston head portions 16 and '26 whereby the pressure in the pumping chambers 19 and 29 will 'be four times the pressures in the motor chambers 18 and 28, respectively.

The pumping chamber 419 is connected by a' passage 30 to a one-way inlet check valve 32. The pumping chamber 29 is connected by a passage 34 with a one-way inlet check valve 36. The inlet sides of the check valves 32 and 36 communicate with a conduit 38 which is connected to a suitable reservoir of hydraulic fluid, not

shown. The pumping chambers 19 and 29 are connected j to passages 40 and 42, respectively, which connect With' a pressure regulator valve 50 which is operable to maintain a substantially constant pressure of hydraulic fluid at the outlet thereof.

The motor piston heads 14 and 24 are interconnected by aplurality of circumferentially spaced rods 52 so that the pistons move simultaneously in the same direction. The rods 52 are attached to through passages 54 and 56 so that the back sides of the motor piston heads 14 and 24 are connected to exhaustchamber 58 at all times. In addition, one of the rods 52 has attached thereto a valve actuator 60 comprising a T-shaped member for mechanically operating a pair of reciprocating pilot valves 52 and 64. The pilot valves the system. The pressure 7 of the hydraulic fluid in the conduit 48 is determined by the piston heads and extend 62 and 64 are supported for reciprocable movement in valve guides 66 and 68, respectively, having shoulders 67 and 69 which limit inward movement of the pilot valves.

The pilot valve 62 has three axially spaced lands 70, 72 and 74 and an actuating rod end portion 78. The pilot valve 64 likewise has three axially spaced lands 80, 82 and 84 and an axially extending rodportion 88. .The rod 88 of the pilot valve 64 can be engaged. by .endl63 of the valve actuator 60 adjacent the stroke.end'of1the piston 12. The rod 78 of the pilot valve. 62 can be engaged by end 61 of the actuator 60adjacent the stroke end of the piston 22.

Gas from any suitable source for actuating the motor pistons is supplied through conduit 90, the pressure-of the gas being controlled by.a relief valve. 92, the outlet side of which is connectedto an exhaust conduit 93. The conduit 90 connects with .an inlet port 9501 a reversing servo actuated valve 94. .The'servo actuated reversing valve 94 is reciprocable in. a valve guide 96 and has three axially spaced lands 98, 100. and 102. The end portions 99 and 103 of the lands 98..and 102 constitute piston surfaces for effecting movement of the reversing valve 94 between its limit positions. The-valve guide 96 is also formed with control ports 104 and 106 which communicate at all times with the annular grooves between lands 98 and 100, and lands100 and- 102, respectively. The port 104 is connected to a passage 108 which communicates with the motor chamber 18. The control port 106 is connected .to a conduit 110 that connects with themotor chamber 28.

Branch passages 112 and 114 communicate 'Wiih the .conduit90, and terminate in ports 116-and 118, respectively, of the pilot valves 62 and 64. The reversing valve 94 also? includes exhaust ports 120 and 122 which connect with an exhaust passage 125. The exhaust gas passage 125 communicates at all times with the chamber 58 as well as with ports 124 and 126 of the pilot valves 62- and 64, respectively. The pilot valves 62 and 64 also include ports 128 and 130 respectively, which are connected to passages132 and 134, respectively.

The passage 132 connects with a passage 136. .One

' end of passage 136 connects with the left-hand end of the valve guide 96, and the other end of the passage 136 connects with the right-hand end of the valve guide 68. The passage 134 connects with a passage 138. One end of the passage 138 connects with the right-hand endofthe valve guide 96, and the otherend of the passage 138 connects with the left-hand end of the valve-guide 66. Accordingly, when the left-hand end of the'valve' guide 96 is subjected to pressure so as to move -.the'.reversing valve 94 to theposition shown in Figure 1; the right-hand end of the valve guide 68 will be subjected to the same pressure so as to move the pilot valve 64 to the position shown in Figure 1 wherein land 84 engages shoulder-69.

At this time, the passage 138 is-connected to exhaust through ports 130 and 126.

Operation of the pump system disclosed in Figure l is as follows. With gas under a pressure-of'between 700 and 800 psi. being supplied to inlet conduit 90, this gas will flow through the supply port 95 of the reversing valve 94. The relief valve 92 may be calibrated to open at 7 50 psi. so that when the pressure of the incoming gas exceeds 750 psi, the relief valve 92 will open and by-pass a portion thereof to the exhaust conduit 93. With the reversing valve 94 in the position of Figure 1, the gas under pressure will flow through supply port 95 to control port 104 and thence through passage 108 to the motor chamber 18. The piston assembly 12 will move to-the right as viewed in Figure 1 thereby etfecting movement of the piston assembly- 22 to the right through the rods 52. Hydraulic fluid which is previouslydrawn intothe pumping chamber 19 through'inlet check valve 32- will i be delivered through the passage-40' and the outlet check valve 44 to the delivery conduit '48. Since-thepressure of the actuating gas remains substantially constant, and since the area of the piston head 14 is four times the area of the piston head 16, the hydraulic fluid will be delivered at a pressure of substantially 3000 psi With the reversing valve 94 in the position of Figure l, the motor chamber 28 is connected to exhaust through passage 110, ports 106 and 122 and the passage 125. During movements of the piston assembly 22 tothe right, the pumping chamber 29 will :be expanded andthereby draw hydraulic fluid from inlet conduit 38through check valve 36 and passage 34 into the pumping chamber'29.

During the power stroke of the piston assembly 12 to the right, the end 63 of the valve actuator 60 will engage the end 88 of 'thepilotvalve -64-as shown in Figure 1. During continued movement of the piston assembly 12 to the right, the pilot valve64 will be moved to the right so that at the stroke end of the piston assembly 12 the ports 118 and 130 will be interconnected by the annular groove between:lands 82andl84. rMovement of the pilot valve 64 to a position whereinports 118: and 130 are interconnectedwillldirect incoming-.gasiunder pressure from passage 114 through ports 1'18 and 130to passage 134. This gas will fiowithrough passage 138 and act on the end surface 103 of the reversing valve to move the reversing valve94 to the left :soas to interconnect ports and106 and connect :port 104 to the exhaust port 120. At the same time, gas under pressure will act through passages 134 and 138 came end face of land 70 of the *pilot valve-62 so as to movethe pilot valve 62 to the right as viewed in Figure 1 until land 74 engages shoulder 67. The pilot valve 62 will be'moved to a position wherein ports 128 and 124 are interconnected and port 116 is blocked by land 72. In this manner, the left-hand end of the valve. guide 96 will be connected to exhaust through passages 136 and 132 and ports 128 and 124.

When the reversing valve 94 has moved to the left, gas -underpressure-will be supplied through ports 95 and 106 to the passage to the motor chamber 28, and at the same time the motor chamber 18 will be connected to exhaust through passage 108 and ports 104 and 120. Ac-

cordingly, the pistonunits 22 and 12 will move to the left thereby completing the delivery stroke of the pumping piston 26 and effecting the-intake stroke of the pumping piston 16. The-pistons 12 and 22will be maintained in a .state of continuous reciprocation as long as gas under pressure is supplied to-the inlet conduit90 and hydraulic fiuid-pumpedby the pumping pistons 16 and 26 is used by the system connected with-the delivery conduit-48. If

the'hydra'ulic system connected-to the conduit 48 does not require any' -flow, movement of the pistons will continue at a rate sufficient to maintain the system pressure. The pressure regulating valve-50 will maintain a pressure of substantially 3000-p.s.i. in thesystem and dump the excess Withparticular reference to 'Figure 2, a modified gas driven hydraulic pump is disclosed for use in systems wherein the gas supplyis under a higher pressure, for instance 1000 psi. The system disclosed'in Figure 2 is of the partial admission type, andthus the motor chambers 18 and 28 are formed with ports 140 and 142, re-

' spectively, which' connect with passages -144and 146.

. 160..andi162. as wellas oppositelyextending .rod portions 164.and 166. The .rod, portion. 164 is engageablewith an abutment/168 --which is :biased to the right as viewed in Figure 2, by.a coil-spring 170. :The rodportion 166 .L15 .engageable with .an abutment. l72 which is biased .to the jllfift, as viewedin Figurel, by a' spring 173. The springs -170xand 173 are disposed in-chamhers-1-74:and 1 76 re- 'spectively, which are connected to the exhaust conduit 125. I v

The ports 140 and 142 in the motor chambers 18 and 28 are locatedso that they will be opened by their respective motor pistons 14 and 24 when the power pistons have completed approximately 80% of their power stroke movement. Accordingly, if gas is supplied through conduit 90 at 1000 psi. to the motor chamber 18,.upon opening of the port 140 gas will be suppliedto passage 144 and will act on the end surface of land 158 to move the shuttle valve 152 to the position, of Figure 2. This movement of the shuttle valve 152 will block the passage 108 thereby cutting off further admission of the gas to the motor chamber 18. The gas in motor chamber 18 will now expand to complete the stroke of the power piston 14 so that at the end of its power stroke the pressure in chamber 18 may be on the order of 800 p.s.i. At the end of the stroke of the motor piston 14, the valve actuator 60 will move the pilot valve 64 to a position wherein ports 118 and 130 are interconnected to thereby effect movement of the reversing valve 94 to the left so that gas under pressure will be supplied to the motor chamber 28 while the motor chamber 18 is connected to exhaust. This movement of the reversing valve will also connect port 150 toexhaust through port 148. The motor piston 24 will'then effect the delivery stroke of the pumping piston 26 and the intake stroke of the pumping piston 16. When the port.142 is uncovered, gas will be supplied through passage 146 and port 156 to act on the end of land 162. In this manner the shuttle valve 152 will be moved to the left so that land 162 will block the passage 1'10 whereupon the gas in motor chamber 28.will expand thereby automatically reducing the pressure in the motor chamber 28.

With reference to Figure 3, a modified gas driven hydraulic pump is shown wherein the inertia efiects of the reciprocating pistons are neutralized. To accomplish this result,'the system includes a second set of motor and pumping piston assemblies which move in a direction opposite 'to that of the first set of motor and pumping piston assemblies. Thus, the pump includes a second set of opposed stepped diameter cylinders and 20 having piston assemblies 12' and 22' disposed for reciprocable movement therein. The piston assemblies include motor pistons 14' and 24' and pumping pistons 16 and 26', which divide their respective cylinders into motor chambers 18 and 29 and pumping chanbers 19 and 29. The motor pistons 14 and 24 are interconnected by a plurality of rods 52' so as to move simultaneously in the same direction.

The pumping chamber 19' is connected by passages 30 and 40' to the inlet and outlet check valves 36 and 46, respectively. The pumping chamber 29 is connected by passages 34' and 42' to inlet and outlet check valves 32 and 44. The motor chamber 18 is connected to the passage 110 and the motor chamber 28 is connected to :the passage 108. The pilot valves and reversing valves :are controlled by the piston assemblies 12 and 22, as in the first embodiment, the arrangement being such that when gas under pressure is supplied to the motor chamber 18 so as to effect movement of the pistons 12 and 22 to the right, gas will be supplied to the motor chamber 28 so as to effect movement of the pistons 12' and 22 to the left. Conversely, when the pistons 12 and 22 are moved to the left, the pistons 12 and 22' are moved to the right so as to neutralize the reciprocating inertia effects of the piston assemblies. Operation of the system disclosed in Figure 3 is believed to be readily apparent since the control valves are identical to those described in connection with Figure 1. The pumping system of Figure 3 will, of course, supply hydraulic fluid under pressure in volumes substantially twice that of the system depicted in Figure 1.

While the embodiments of the invention as herein disclosed constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows: Y

1. A gas driven hydraulic pump including, a pair of opposed cylinders, a piston mounted for reciprocation within each cylinder, means interconnecting said pistons for simultaneous movement in the same direction, said pistons div'iding their respective cylinders into a motor vchamber and ap mping chamber, inlet. and outlet check valves communicating with each pumping chamber, .reversing valve means for controlling the alternate admission and exhaust of gas under pressure to the opposed motor chambers, a spring centered servo actuated shuttle valve controlled by movement of each piston for cutting off the supply of gas under pressure to its respective motor chamber during the power stroke thereof to permit expansion of the gas in said motor chamber to complete the power stroke of said piston, and means for actuating said reversing valve adjacent the stroke ends of said pistons.

2. A gas driven hydraulic pump including, a pair of opposed cylinders of stepped diameter, a piston having head portions of dilferent diameters mounted for reciprocation within each cylinder, means interconnecting said pistons for simultaneous movement in the same direction, each piston dividing its respective cylinder into a motor chamber and a pumping chamber, a servo actuated reversing valve operatively connected with said motor chambers for controlling the alternate admission and exhaust of gas under pressure to the opposed motor chambers, a servo actuated shuttle valve connected between said reversing valve and said motor chambers for cutting off the admission of gas under pressure to each motor chamber after a predetermined movement of each piston during its power stroke, a pair of pilot valves operatively connected with said reversing valve for controlling the position of said reversing valve, and a valve actuator constrained for movement with said pistons and engageable I with said pilot valves for actuating said pilot valves adjacent the stroke ends of said pistons.

3. A gas driven hydraulic pump including, a pair of opposed cylinders, a piston mounted for reciprocation within each cylinder, means interconnecting said pistons for simultaneous movement in the same direction, each piston dividing its respective cylinder into a motor chamber and a pumping chamber, reversing valve means actuated by said pistons for controlling the alternate admission and exhaust of gas under pressure to the opposed motor chambers adjacent the stroke ends of said pistons, a shuttle valve connected between said reversing valve means and said motor chambers having a pair of oppositely acting pressure responsive surfaces, spring means normally centering said shuttle valve so that the reversing valve controls the admission of gas under pressure to said motor chambers, and means connecting said opposed pressure responsive surfaces with piston controlled ports in said motor chambers whereby said shuttle valve will be pressure actuated to cut off the supply of gas under pressure during the power stroke of each piston to permit expansion of the gas in the respective motor chamber to complete the power stroke of each piston.

4. A gas driven hydraulic pump including, a pair of opposed cylinders, a piston mounted for reciprocation within each cylinder, means interconnecting the piston for simultaneous movement in the same direction, each piston dividing its respective cylinder into a motor chamber and a pumping chamber, piston actuated reversing valve means for controlling the alternate admission and exhaust of gas under pressure to the opposed motor chambers adjacent the stroke ends of said pistons, said reversing valve means including a pair of control ports, passage means connecting said control ports with said motor chambers, a shuttle valve disposed within said passage means and operable to control the admission of gas under pressure to each motor chamber, said shuttle valve having a pair of opposed pressure responsive surfaces,

spring means normally centering said shuttle valve enabling the reversing valve means to control the admission of gas under pressureto said'motor chambers; eachmotor chamber having a piston controlled port, and passage means connecting said motor' chamber "ports with said opposed pressure responsive surfaces-whereby said-pressure responsive surfaces will be-alternately subjected to gas underpressureduring thepower strokes-of saidpistons for cutting off'the supply of gas under pressureto the motor chambers during the power strokes of said 710 '2;799,444

pistons to permit the expansion of gas in said motor chambers to-complete the power strokes of saidpistons.

References Cited in thefile of thisppatent 'VUNITED STATES PATENTS 2,239,727 Mayer "Apr. 29, 1941 2;296,647 McCormick Sept.'22,1942 'Schemmel 'uly'16, 1957 .a my t u a 

